The satisfactory removal of greasy soils/stains, that is soils/stains having a high proportion of triglycerides or fatty acids, is a challenge faced by the formulator of detergent compositions for use in laundry and dish washing methods. Surfactant components have traditionally been employed in detergent products to facilitate the removal of such greasy soils/stains. In particular, surfactant systems comprising cationic esters have been described for use in greasy soil/stain removal.
A particular challenge to the formulator of detergent compositions for use in a laundry washing method is the satisfactory removal of bleachable soils/stains such as tea, fruit juice and coloured vegetable soils from stained fabrics. It is known that stained fabrics have a tendency to present a `dingy` appearance after frequent washing. Bleaches are traditionally employed in detergents to remove the bleachable stains or soils, and also those responsible for the `dingy` appearance of the fabric. It is well established that peroxygen bleaches and bleaching systems, based on organic peroxyacids can provide stain and/or soil removal from fabrics. The organic peroxyacids are often obtained by the in situ perhydrolysis of organic peroxyacid bleach precursor compounds (bleach activators). To remove greasy stains/soils, which are of hydrophobic nature, hydrophobic organic peroxyacids can be employed in detergent products. Such organic peroxyacids generally comprise long chain (&gt;7 carbon atoms) alkyl moieties. Hydrophobic bleaches are known to have a tendency to migrate rapidly to the surface of fabrics under wash conditions.
Bleaches which may be hydrophobic are disclosed for example in EP-A-0170386. It is stated that these bleaches may be used in compositions which incorporate different types of surfactant materials. Anionic, nonionic, zwitterionic and amphoteric surfactants are disclosed. Hydrophobic bleaching agents are also described in WO95/3226 as useful suds suppressants in detergent compositions containing high levels of surfactant.
Quaternary ammonium compounds are known cationic surfactants. For example in GB-A-2040990 alkoxylated nonionic and cationic surfactants and anionic surfactants are used in combination to produce detergents for fabric washing.
It has now been found that a problem with hydrophobic bleaches is that despite their tendency to migrate to the fabric surface, they do not necessarily interact fully with the stain or soil components. It has been found that the hydrophobic bleaches can be prevented from migration onto the greasy stains/soils by deposited `lime soaps` (formed by alkaline earth ions with fatty acids, present in the wash solution) on the fabric. Thereby, their bleaching performance can be diminished. This result in a lessening of the dingy soil cleaning performance of the hydrophobic bleach.
The Applicants have found that this problem can be ameliorated by use of a particular combination of cationic surfactant and bleach resulting in a surprising enhancement of the bleach efficacy of the hydrophobic organic peroxyacid bleaching system. Thereby, the overall cleaning performance of the detergent are improved.
Three mechanisms are believed to be responsible for this unexpected benefit. First, the cationic surfactant is capable of reducing `lime soap` deposition on the fabric surface, thereby facilitating the partition of the hydrophobic organic bleaches into the greasy stains/soils. Secondly, the cationic surfactant reduces the surface tension between the fabric and the wash solution. Thereby, the interaction with the greasy stains/soils on the fabric by the hydrophobic organic bleach agent will be facilitated. Thirdly, the cationic surfactant and the negatively charged hydrophobic organic peroxyacids, formed in the wash, can form a non-polar associated couple, which will partition rapidly into hydrophobic, greasy stains/soils on the fabric.
All documents cited in the present description are, in relevant part, incorporated herein by reference.